Carbon canisters are commonly used to store purge vapor from a fuel tank until the purge vapor can be disposed of. Most vehicles have an evaporative emission control (EVAP) system that is used to remove purge vapor from the canister, and transfer the purge vapor to the engine, where the purge vapor is burned off during combustion. One type of EVAP system uses manifold vacuum to draw air through the canister and pull the vapors into the engine. However, systems which use manifold vacuum may not always generate enough vacuum to draw sufficient amounts of air through the canister to pull the purge vapor into the engine. With turbocharged engines, the manifold pressure is used with a venturi-style of nozzle to create a vacuum for purging. The drawback to this approach is that directing pressurized air away from the turbocharger for use in purging, reduces the efficiency of the turbocharger and reduces the amount of power increase to the engine.
Accordingly, there exists a need for an evaporative emission control system that provides for sufficient transfer of purge vapor to the engine, without sacrificing engine efficiency.